Regenerated alloy material based on chemical and physical co-modification and method for preparing same

ABSTRACT

The present invention discloses a regenerated HIPS/PPO alloy material based on chemical and physical co-modification, which is mainly composed of the following components in parts by mass: waste HIPS 60-70, PPO 30-40, HIPS-based macromolecular chain extender 2-8, elastomer toughening agent 2-10, oxazoline chain extender 0.2-1, and chain-extension catalyst 0.1-0.4. The alloy material uses chemical modification of in-situ chain extension and compatibilization of the macromolecular chain extender to restore a molecular chain structure, improve a phase interface and increase compatibility of the alloy. Through physical modification introduced by adding the elastomer toughening agent, a combined effect of chemical modification and physical modification is exploited, with target properties improved, a regenerated plastic alloy material with an excellent comprehensive property prepared, and the waste fully utilized to achieve energy saving and emission reduction. A method for preparing the above-described alloy material is also disclosed.

TECHNICAL FIELD

The present invention belongs to the technical field of waste HIPSregeneration, and specifically relates to a regenerated alloy materialbased on chemical and physical co-modification and a method forpreparing same.

DESCRIPTION OF RELATED ART

High impact polystyrene (HIPS) is widely used in the preparation ofplastic housings for electronic devices such as air-conditioningcabinets and television sets due to its excellent comprehensiveproperty. The main advantages of HIPS include high impact strength, goodgloss, good heat resistance and flowability, etc. However, thedegradation of HIPS may occur during processing and use, leading tochain scission of molecular chain and change of phase structure,resulting in that the property of waste HIPS is far worse than that ofnew HIPS.

Polyphenylene oxide (PPO) has the advantages of high rigidity, high heatresistance, flame resistance, high strength and excellent electricalproperties, but its fluidity is poor and viscosity is sensitive totemperature, so that the molding temperature should be strictlycontrolled. PPO is suitable for manufacturing heat-resistant parts,insulation parts, wear-reducing and resistant parts, transmission parts,medical and electronic parts, etc. and is widely used in automotiveindustry, electronic and electrical devices, office equipment, precisionequipment, textile equipment, etc.

The alloying of polymer materials can combine the superior properties ofmatrix materials to achieve high value applications, so that it is alsoan important research and application direction. It has cost advantageto prepare high molecular alloy from waste materials, but it isnecessary to repair the properties of waste materials effectively toprepare regenerated alloy materials with market demand. Blending newmaterials of HIPS with PPO not only improves the strength of HIPS, butalso improves the fluidity of PPO due to the good compatibility betweenthe two. However, the compatibility of HIPS/PPO blends is negativelyaffected by the aging and degradation of HIPS and the change ofmolecular structure and polarity during use.

In combination with the above-mentioned status quo, if the waste HIPSand PPO can be used to prepare a polymer alloy, the active groups suchas hydroxyl group and carboxyl group generated after the waste HIPSaging can be fully used. The waste HIPS can be initially repairedthrough molecular chain extension and similar compatibility. Thecomprehensive property of the waste HIPS base material can becomprehensively improved, and the compatibility of the waste HIPS andPPO can be effectively improved at the same time. A regenerated alloymaterial with excellent comprehensive property can be obtained throughthe physical modification of a combination toughening agent with thejoint action of chemical modification and physical modification fullyused. Due to the large use of waste materials, this material has theadvantages of cost-effective and environmental properties, and has broadapplication prospects.

SUMMARY

The object of the present invention is to provide a regenerated alloymaterial based on chemical and physical co-modification, wherein theregenerated HIPS/PPO alloy material uses the chemical modification ofin-situ chain extension and compatibilization of a macromolecular chainextender to repair a molecular chain structure, improve a phaseinterface and increase a compatibility. On the basis of the initialimprovement of the micro-properties and macro-mechanical properties ofwaste materials, with the physical modification effect introduced bycombining and adding an elastomer toughening agent, the combined effectof chemical modification and physical modification is fully exploited,and the target properties are further improved. Finally, a regeneratedplastic alloy material with an excellent comprehensive property isprepared, and the waste is fully utilized to achieve energy saving andemission reduction.

It is also an object of the present invention to provide a method forpreparing the regenerated alloy material based on chemical and physicalco-modification as described above.

The above-mentioned first technical problem of the present invention isachieved by the following technical solution: a regenerated alloymaterial based on chemical and physical co-modification, mainly composedof the following components in parts by mass:

-   -   a waste HIPS: 60-70;    -   a PPO: 30-40;    -   a HIPS-based macromolecular chain extender: 2-8;    -   an elastomer toughening agent: 2-10;    -   an oxazoline chain extender: 0.2-1; and    -   a chain-extension catalyst: 0.1-0.4.

Among the above-described components of the regenerated alloy materialbased on chemical and physical co-modification:

The HIPS-based macromolecular chain extender is preferably a high impactpolystyrene grafted a maleic anhydride (HIPS-g-MAH).

The elastomer toughening agent is preferably astyrene-ethylene-butylene-styrene block copolymer (SEBS).

The oxazoline chain extender is preferably a2,T-(1,3-phenylene)-bisoxazoline (PBO).

The chain-extension catalyst is preferably a 4-dimethylamino pyridine(DMAP).

The waste HIPS is preferably a flake material obtained after crushingand homogenizing the waste HIPS.

The PPO is a polyphenylene ether.

The above-mentioned second object of the present invention is achievedby the following technical solution: a method for preparing theregenerated alloy material based on chemical and physicalco-modification, comprising the steps of: mixing the waste HIPS, thePPO, the HIPS-based macromolecular chain extender and thechain-extension catalyst according to the above-mentioned dosagerelationship to obtain a mixture material, adding the mixture materialfrom a main feeding device of a twin-screw extruder to melt, controllinga screw rotation speed to 60-90 rpm, adding the oxazoline chain extenderand the elastomer toughening agent from a fourth processing zone of thetwin-screw extruder according to the above-mentioned dosage relationshipto blend with a melted mixture material, and then extruding, drawing,cooling and pelletizing to obtain the regenerated HIPS/PPO alloymaterial.

In the method for preparing the regenerated alloy material based onchemical and physical co-modification:

A processing temperature range of the twin screw extruder is preferablyat 225-255° C.

Further, temperatures of six processing zones of the twin-screw extruderare preferably successively 225° C., 230° C., 230° C., 235° C., 255° C.,and 255° C.

The HIPS-based macromolecular chain extender added in the presentinvention can simultaneously play three key roles.

(1) The reactive anhydride groups on the molecular chain and thehydroxyl groups generated on the aged chain of waste HIPS can occur anin-situ chain-extension reaction under extrusion conditions to achievechain extension of waste HIPS, thereby repairing the initial molecularstructure of waste and greatly improving the macro property of HIPSsubstrate.

(2) The structure of HIPS backbone of HIPS-based macromolecular chainextender is similar to that of waste HIPS structure, which is veryhelpful to improve the microstructure of waste HIPS after aging anddecrease an interfacial force, and then promote the compatibility ofHIPS phase and PPO phase.

(3) The HIPS-based macromolecular chain extender contains a certainamount of PB (polybutadiene) component, and the addition of theHIPS-based macromolecular chain extender is also equivalent toincreasing an overall gel content of the regenerated alloy material,which exhibits a toughening function.

The chain-extension catalyst in the present invention is highlynecessary. Since the processing temperature of PPO is higher and thestability of waste HIPS is lower than that of fresh HIPS, the waste HIPScomponent is likely to be degraded under the classical PPO processingconditions, i.e. long-term processing at a higher processingtemperature, thereby affecting the overall properties of the regeneratedalloy. Therefore, in order to avoid the degradation of waste materialsand ensure the efficient progress of the chain-extension reaction, thechain-extension reaction is promoted by adding a chain-extensioncatalyst to reduce the extrusion time and lower the extrusiontemperature.

The oxazoline chain extender added in the present invention is acarboxyl-reactive chain extender under extrusion processing conditions.In order to further enhance the chain extension modification effect, ananhydride-type HIPS-based macromolecular chain extender, which can reactwith hydroxyl groups in the aged molecular chain of the mixed system andcomplementarily generates new carboxyl groups to increase the chainextension potential of the subsequent use of the oxazoline chainextender, is firstly added from the main feeding device. Then theoxazoline chain extender is added into a feeding port in a middle of abarrel of the fourth zone to realize a stepwise reaction by feedingseparately, such that an in-situ chain extension repair can be fully andeffectively performed and the excessive consumption, which is caused bydirect reaction between anhydride and oxazoline group when HIPS-basedmacromolecular chain extender and oxazoline chain extender are blendeddirectly and thus affects the chain extension repair of backbone of thewaste HIPS, can be avoided.

The elastomer toughening agent SEBS added in the present invention is aphysical modifier of elastomer with ultra-high toughness and relativelylow strength, which mainly neutralizes and improves the impact strengthof the whole blend system through its own very high toughness. Theelastomer toughening agent SEBS has good compatibility with HIPS and PPOand does not contain unsaturated carbon-carbon double bond which wouldeasily lead to the decrease of aging resistance of regenerated products.As such, it is a better choice of the toughening agent for regeneratedHIPS/PPO alloy. On the other hand, since the property that deterioratesthe most seriously due to aging of waste HIPS is the impact strength(retention values of tensile strength and bending strength after agingare relatively high), while the other component PPO intrinsically hasthe characteristics of large rigidity, large strength and generaltoughness, toughening the regenerated HIPS/PPO alloy is very beneficialto improve its disadvantageous property, thus effectively broadening theapplication range.

It has been mentioned previously that temperature and screw rotationspeed have a large effect on the comprehensive property of theregenerated alloy. Longer extrusion retention times and highertemperatures are beneficial to promote in-situ chain-extension reactionsduring extrusion and to make the blending more homogeneous, but overlylong processing times and overly high temperatures may lead todecomposition of the regenerated material. Through a large number ofexperiments, it is proved that, based on the function of chain-extensioncatalyst, controlling the screw rotation speed to 60-90 rpm andprocessing temperature range of 225-255° C. can provide an effectiveblending and avoid the decomposition of regenerated materials withoutaffecting the effect of in-situ chain extension.

Compared to the prior art, the present invention has the followingadvantages.

(1) The present invention uses a combination of two different chainextenders, based on in-situ chain extension and compatibilization, tooriginally and completely enhance the comprehensive property of wasteHIPS and improve the compatibility of the blend.

(2) After the comprehensive property of HIPS-based material is improvedoriginally and completely by in-situ chain extension, SEBS elastomerphysical modifier is further introduced.

Through the co-action of chemical modification and physicalmodification, the toughness of regenerated HIPS/PPO alloy is furtherimproved and its application range is effectively widened.

(3) The whole processing process of the present invention usesconventional plastic processing equipment to perform reaction-typeextrusion by selecting the process and optimizing the formulation, andthus can be conveniently applied and popularized.

(4) The present invention provides a new solution for the high-valueutilization of typical large-scale waste plastics, and also drives thedevelopment of regenerated plastics industry. Meanwhile, the relatedproducts have strong market competitiveness, and are in line withnational energy saving and emission reduction policies, with good socialand economic benefits.

DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS Embodiment 1

The regenerated alloy material based on chemical and physicalco-modification provided in this embodiment is mainly composed of thefollowing components in parts by mass:

-   -   a waste HIPS: 70    -   a PPO: 30    -   a HIPS-based macromolecular chain extender: 8    -   an elastomer toughening agent: 10    -   an oxazoline chain extender: 0.8; and    -   a chain-extension catalyst: 0.4.

The HIPS-based macromolecular chain extender is a high impactpolystyrene grafted maleic anhydride (HIPS-g-MAH). The elastomertoughening agent is a styrene-ethylene-butylene-styrene block copolymer(SEBS). The oxazoline chain extender is a2,2′-(1,3-phenylene)-bisoxazoline (PBO). The chain extension catalyst isa 4-dimethylamino pyridine (DMAP). The waste HIPS is a flake materialobtained after crushing and homogenizing the waste HIPS, and the PPO isa polyphenylene oxide.

The method for preparing the regenerated alloy material based onchemical and physical co-modification comprises the steps of: mixing thewaste HIPS, the PPO, the HIPS-based macromolecular chain extender andthe chain-extension catalyst according to the above-mentioned dosagerelationship to obtain a mixture material, adding the mixture materialfrom a main feeding device of a twin-screw extruder to melt, controllinga screw rotation speed to 60 rpm, adding the oxazoline chain extenderand the elastomer toughening agent from a fourth processing zone of thetwin-screw extruder according to the above-mentioned dosage relationshipto blend with a melted mixture material, and then extruding, drawing,cooling and pelletizing to obtain the regenerated HIPS/PPO alloymaterial.

Temperatures of six processing zones of the twin-screw extruder aresuccessively set to 225° C., 230° C., 230° C., 235° C., 255° C., and255° C.

Embodiment 2

The regenerated alloy material based on chemical and physicalco-modification provided in this embodiment is mainly composed of thefollowing components in parts by mass:

-   -   a waste HIPS: 70    -   a PPO: 30    -   a HIPS-based macromolecular chain extender: 8    -   an elastomer toughening agent: 2    -   an oxazoline chain extender: 0.8; and    -   a chain-extension catalyst: 0.4.

The waste HIPS, the PPO, the HIPS-based macromolecular chain extender,the elastomer toughening agent, the oxazoline chain extender and thechain-extension catalyst are the same as those in Embodiment 1.

The method for preparing the regenerated alloy material based onchemical and physical co-modification comprises the steps of: mixing thewaste HIPS, the PPO, the HIPS-based macromolecular chain extender andthe chain-extension catalyst according to the above-mentioned dosagerelationship to obtain a mixture material, adding the mixture materialfrom a main feeding device of a twin-screw extruder to melt, controllinga screw rotation speed to 60 rpm, adding the oxazoline chain extenderand the elastomer toughening agent from a fourth processing zone of thetwin-screw extruder according to the above-mentioned dosage relationshipto blend with a melted mixture material, and then extruding, drawing,cooling and pelletizing to obtain the regenerated HIPS/PPO alloymaterial.

Temperatures of six processing zones of the twin-screw extruder aresuccessively set to 225° C., 230° C., 230° C., 235° C., 255° C., and255° C. Embodiment 3

The regenerated alloy material based on chemical and physicalco-modification provided in this embodiment is mainly composed of thefollowing components in parts by mass:

-   -   a waste HIPS: 60;    -   a PPO: 40;    -   a HIPS-based macromolecular chain extender: 4;    -   an elastomer toughening agent: 4;    -   an oxazoline chain extender: 0.4; and    -   a chain-extension catalyst: 0.2.

The waste HIPS, the PPO, the HIPS-based macromolecular chain extender,the elastomer toughening agent, the oxazoline chain extender and thechain-extension catalyst are the same as those in Embodiment 1.

The method for preparing the regenerated alloy material based onchemical and physical co-modification comprises the steps of: mixing thewaste HIPS, the PPO, the HIPS-based macromolecular chain extender andthe chain-extension catalyst according to the above-mentioned dosagerelationship to obtain a mixture material, adding the mixture materialfrom a main feeding device of a twin-screw extruder to melt, controllinga screw rotation speed to 90 rpm, adding the oxazoline chain extenderand the elastomer toughening agent from a fourth processing zone of thetwin-screw extruder according to the above-mentioned dosage relationshipto blend with a melted mixture material, and then extruding, drawing,cooling and pelletizing to obtain the regenerated HIPS/PPO alloymaterial.

Temperatures of six processing zones of the twin-screw extruder aresuccessively set to 225° C., 235° C., 235° C., 240° C., 255° C., and250° C.

The mechanical properties of the alloy material based on chemical andphysical co-modification prepared in Embodiments 1-3 are summarized inTable 1 below.

TABLE 1 Summary of Mechanical Properties of Regenerated HIPS/PPO AlloyMaterials Prepared in Embodiments 1-3. Bending Impact Tensile strengthstrength strength (MPa) (KJ/m²) (MPa) GB/T 9341 GB/T 1043 GB/T 1040waste HIPS/ 62.5 3.6 46.2 PPO 

Embodiment 1 66.1 12.7 51.6 Embodiment 2 70.1 9.5 53.9 Comparative 71.57.7 56.1 example 1 

Embodiment 3 68.5 10.5 54.9 Comparative 70.3 7.5 58.4 example 2 

In Table 1:

{circle around (1)} The preparation method and steps are the same asthose in embodiment 1. The material ratio is 70 parts of waste HIPS and30 parts of PPO, and no HIPS-based macromolecular chain extender,elastomer toughening agent, oxazoline chain extender and chain-extensioncatalyst are contained.

{circle around (2)} The preparation method and steps are the same asthose in Embodiment 1 and Embodiment 2. The material ratio is 70 partsof waste HIPS, 30 parts of PPO, 8 parts of HIPS-based macromolecularchain extender, 0.8 part of oxazoline chain extender and 0.4 part ofchain-extension catalyst, and no elastomer toughening agent iscontained.

{circle around (3)} The preparation method and steps are the same asthose in Embodiment 3. The material ratio is 60 parts of waste HIPS, 40parts of PPO, 4 parts of HIPS-based macromolecular chain extender, 0.4part of oxazoline chain extender and 0.2 part of chain-extensioncatalyst, and no elastomer toughening agent is contained.

It can be seen from the above-mentioned specific experimental data that,compared to the unmodified waste HIPS/PPO, the mechanical properties ofthe regenerated HIPS/PPO alloy prepared by the present invention areimproved overall, and especially the improvement of the impact strengthwhich is more sensitive to the molecular weight of the backbone, thestructure of the molecular chain and the effect of the phase interfaceis particularly obvious.

Embodiment 1 differs from Embodiment 2 in that different amounts of theelastomer toughening agent are added, and it can be seen fromEmbodiments 1-2 that when the elastomer toughening agent is added in arelatively high amount, the impact strength of the alloy material can begreatly increased.

The difference between Embodiments 1-2 and Comparative example 1 is theaddition of an elastomer toughening agent of ultra-high toughness andlower strength. In Embodiment 1, with chemical and physicalco-modification, the impact strength is greatly increased by 65% and thebending and tensile strengths are only slightly decreased by about 8%(while the impact, bending and tensile strengths are increased by 253%,6% and 12%, respectively, compared to the unmodified waste HIPS/PPO),and the comprehensive property is very good.

Embodiment 3 also had a similar comparative effect with Comparativeexample 2. Since the property that deteriorates the most seriously dueto aging of waste HIPS is the impact strength (wherein retention valuesof tensile strength and bending strength after aging are relativelyhigh), while the other component PPO intrinsically has thecharacteristics of large rigidity, large strength and general toughness,toughening the regenerated HIPS/PPO alloy has the disadvantageousproperty of impact strength.

Therefore, the present invention is based on chemical and physicalco-modification, and is very beneficial to improve the environmentaladaptability of regenerated products and widen the application scenariosthereof by very limitedly and slightly reducing the non-disadvantageousproperties (strength properties) such as the tensile strength and thebending strength in exchange for great improvement in thedisadvantageous property (toughness property) such as the impactstrength. The regenerated alloy products with this comprehensiveproperty have good market prospects.

The above-mentioned embodiments are preferred embodiments of the presentinvention, and the PPO, HIPS-based macromolecular chain extenderHIPS-g-MAH, the elastomer toughening agent SEBS, the oxazoline chainextender PBO and the chain-extension catalyst DMAP selected in theembodiments are all obtained from commercially available products.

However, the implementations of the present invention are not limited tothe above-mentioned embodiments, and the waste HIPS, the PPO and otherraw materials selected in the above-mentioned embodiments may also becommercially available ready-made products with similar properties.Changes, modifications, substitutions, combinations, and simplificationswhich do not depart from the spiritual substances and principles of thepresent invention are all equivalent alternatives and are intended to beincluded in the scope of protection of the present invention.

1. A regenerated alloy material based on a chemical and physicalco-modification, being composed of the following components in parts bymass: a waste HIPS: 60-70; a PPO: 30-40; a HIPS-based macromolecularchain extender: 2-8; an elastomer toughening agent: 2-10; an oxazolinechain extender: 0.2-1; and a chain-extension catalyst: 0.1-0.4.
 2. Theregenerated alloy material based on the chemical and physicalco-modification according to claim 1, wherein the HIPS-basedmacromolecular chain extender is a high impact polystyrene graftedmaleic anhydride (HIPS-g-MAH).
 3. The regenerated alloy material basedon the chemical and physical co-modification according to claim 1,wherein the elastomer toughening agent is astyrene-ethylene-butylene-styrene block copolymer (SEB S).
 4. Theregenerated alloy material based on the chemical and physicalco-modification according to claim 1, wherein the oxazoline chainextender is a 2,2′-(1,3-phenylene)-bisoxazoline (PBO).
 5. Theregenerated alloy material based on the chemical and physicalco-modification according to claim 1, wherein the chain-extensioncatalyst is a 4-dimethylamino pyridine (DMAP).
 6. The regenerated alloymaterial based on the chemical and physical co-modification according toclaim 1, wherein the waste HIPS is a flake material obtained aftercrushing and homogenizing the waste HIPS.
 7. A method for preparing theregenerated alloy material based on a chemical and physicalco-modification according to claim 1, comprising: mixing the waste HIPS,the PPO, the HIPS-based macromolecular chain extender and thechain-extension catalyst to obtain a mixture material; adding themixture material from a main feeding device of a twin-screw extruder tomelt, and controlling a screw rotation speed to 60-90 rpm; adding theoxazoline chain extender and the elastomer toughening agent from afourth processing zone of the twin-screw extruder to blend with a meltedmixture material; and extruding, drawing, cooling and pelletizing toobtain the regenerated alloy material.
 8. The method for preparing theregenerated alloy material based on the chemical and physicalco-modification according to claim 7, wherein a processing temperaturerange of the twin screw extruder is at 225-255° C. .
 9. The method forpreparing the regenerated alloy material based on the chemical andphysical co-modification according to claim 8, wherein temperatures ofsix processing zones of the twin-screw extruder are successively 225°C., 230° C., 230° C., 235° C., 255° C., and 255° C.
 10. A method forpreparing the regenerated alloy material based on a chemical andphysical co-modification according to claim 2, comprising: mixing thewaste HIPS, the PPO, the HIPS-based macromolecular chain extender andthe chain-extension catalyst to obtain a mixture material; adding themixture material from a main feeding device of a twin-screw extruder tomelt, and controlling a screw rotation speed to 60-90 rpm; adding theoxazoline chain extender and the elastomer toughening agent from afourth processing zone of the twin-screw extruder to blend with a meltedmixture material; and extruding, drawing, cooling and pelletizing toobtain the regenerated alloy material.
 11. A method for preparing theregenerated alloy material based on a chemical and physicalco-modification according to claim 3, comprising: mixing the waste HIPS,the PPO, the HIPS-based macromolecular chain extender and thechain-extension catalyst to obtain a mixture material; adding themixture material from a main feeding device of a twin-screw extruder tomelt, and controlling a screw rotation speed to 60-90 rpm; adding theoxazoline chain extender and the elastomer toughening agent from afourth processing zone of the twin-screw extruder to blend with a meltedmixture material; and extruding, drawing, cooling and pelletizing toobtain the regenerated alloy material.
 12. A method for preparing theregenerated alloy material based on a chemical and physicalco-modification according to claim 4, comprising: mixing the waste HIPS,the PPO, the HIPS-based macromolecular chain extender and thechain-extension catalyst to obtain a mixture material; adding themixture material from a main feeding device of a twin-screw extruder tomelt, and controlling a screw rotation speed to 60-90 rpm; adding theoxazoline chain extender and the elastomer toughening agent from afourth processing zone of the twin-screw extruder to blend with a meltedmixture material; and extruding, drawing, cooling and pelletizing toobtain the regenerated alloy material.
 13. A method for preparing theregenerated alloy material based on a chemical and physicalco-modification according to claim 5, comprising: mixing the waste HIPS,the PPO, the HIPS-based macromolecular chain extender and thechain-extension catalyst to obtain a mixture material; adding themixture material from a main feeding device of a twin-screw extruder tomelt, and controlling a screw rotation speed to 60-90 rpm; adding theoxazoline chain extender and the elastomer toughening agent from afourth processing zone of the twin-screw extruder to blend with a meltedmixture material; and extruding, drawing, cooling and pelletizing toobtain the regenerated alloy material.
 14. A method for preparing theregenerated alloy material based on a chemical and physicalco-modification according to claim 6, comprising: mixing the waste HIPS,the PPO, the HIPS-based macromolecular chain extender and thechain-extension catalyst to obtain a mixture material; adding themixture material from a main feeding device of a twin-screw extruder tomelt, and controlling a screw rotation speed to 60-90 rpm; adding theoxazoline chain extender and the elastomer toughening agent from afourth processing zone of the twin-screw extruder to blend with a meltedmixture material; and extruding, drawing, cooling and pelletizing toobtain the regenerated alloy material.